In the clinical field the need to take blood samples safely using needle devices provided with means offering the operator total shielding from the needle after taking the blood sample so as to prevent the risk of accidental contact with the needle itself is strongly felt.
One of the solutions proposed envisages providing the device for taking samples with a mobile protective shield which, mechanically connected to it in a stable manner, can be moved from a non active position, wherein it does not interfere with the needle, and an active position, wherein it encloses the needle within it, thereby shielding it.
A device of this type for taking samples is described, for example, in the European patent EP 56671 B1. The protective shield is connected to the device, in this case, a vial holder, by a flexible tongue H (“living hinge”; as shown in FIG. 1 hereto attached, extracted from EP 56671 B1).
A similar device for taking samples is described in the U.S. Pat. No. 5,207,653. The protective shield is connected to the device, in this case, a needle holder hub, by a hinge. In a first embodiment the screen is hinged to the hub by means of two pins P′ which projecting from said shield snap-fit into two counter-shaped seats P″ made in the hub (as shown in FIG. 2, extracted from U.S. Pat. No. 5,207,653). In a second embodiment the shield is hinged to the hub by means of a single pin M housed in through seats made so as to be aligned on the hub and on the shield (as shown in FIG. 3, extracted from U.S. Pat. No. 5,207,653).
Yet another device is described in the European patent EP 995455 B1. The protective shield is connected to the device for taking samples, in this case, a needle holder hub, by a snap-coupling system. Such system is composed of a U-shaped hook, which, projecting from the needle-holder hub, defines the hinging seat with an open slot, and by a bar B, which projecting from the shield by means of two arms is aligned along the rotation axis and scaled to snap-fasten to the hook in a relation of free rotation acting as a pivot (as shown in FIG. 4, extracted from EP 995455 B1).
The solution described in the European patent EP 56671 B1 (device with flexible tongue) is simple to construct inasmuch as it does not require mechanical couplings of small parts. However this solution has operating limits linked to the fact that, as a result of the shape memory, the flexible tongue tends to resume its original position acquired at the moment of moulding.
This problem does not arise however in those solutions adopting a mechanical type joint.
Of the solutions with a mechanical type joint, the solution of patent EP 995455 B1 (device with snap-fasten, hook-bar system) and the first solution of the U.S. Pat. No. 5,207,653 (device with snap-fasten system composed of two pin-seat pairs, see FIG. 2) also have the advantage of being simple to produce from a constructional point of view. The two parts to be hinged can, in fact, be moulded separately and then subsequently easily assembled to each other.
The two solutions mentioned above are not, however, entirely operationally satisfactory, despite ensuring functionality in terms of safety in protecting the needle when the shield is in the active shielding position. This is due essentially to the fact that the structure of the mechanical joints used in these two solutions does not ensure a stable connection of the protective shield when the latter is in the non active position. In fact, in the case of lateral impact (i.e. directed parallel to the rotation axis of the shield) the shield may be pushed out of the hinging seat and thereby be disconnected from the device.
This happens, in particular, with the solution described in patent EP 995455 B1, i.e. with the device provided with a hook-bar fastening system. The hook defines a hinging seat open all along its axial extension. When the shield is positioned on the open side of the hook (in the non-active shielding position) the two support arms of the bar do not interfere laterally with the hook and cannot therefore prevent lateral shifts of the shield.
The mechanical type joint adopted in the second embodiment of the U.S. Pat. No. 5,207,653 (device with single hinge and through seats, see FIG. 3) ensures rather a stable connection of the shield to the device thanks to the presence of a single hinge extending all along the hinging axis.
This solution has the disadvantage however of being more complicated to produce in terms of construction than the other solutions with mechanical joints. The critical step is the assembly of the components. This operation is difficult not just on account of having to handle small parts (especially the pin), but also due to the fact that assembly of the hinge requires forcing the pin inside the through seats. The pin is in fact scaled to work with an interference relation at least with some sections of the through seats, the interference being essential to prevent the pin from accidentally coming out of the hinging seat and for the shield to rotate freely around the pin by gravity, under its own weight, thereby preventing normal use of the device.